Hydraulic systems, in particular in hydraulic control units of automatic transmissions, typically use a pilot-operated pressure relief valve, hereinafter referred to as system pressure valve, in order to adjust the system pressure in such a manner that the power consumption of the pump of the transmission is not unnecessarily high, and/or that the actuating elements are supplied with at least the amount of pressure that ensures safe operation of the system.
In order to adjust the system pressure, this is typically controlled by a pilot valve in such a manner that it may be continuously adjusted between a minimum pressure that is at least necessary for operation and a maximum pressure that is necessary for safe insertion and for full power transmission of the shift elements.
In hydraulic control units of automatic transmissions, the system pressure range may be varied in such a manner that the maximum and minimum system pressure are found in a very high relationship with each other, by which the valve reinforcement of the system pressure valve between the system pressure and the pilot pressure valve takes on a value of >5. In the low pressure range, this leads in particular to position inaccuracies in a negative manner, which may result in an increased pump absorption torque and thus increased consumption.